(1) Field of the Invention
The present invention relates to an image synthesizing device which outputs, to a video display device, a video in which a graphics object such as a subtitle, a widget, an icon, and an animation is synthesized onto an area of image data obtained by decoding a bit stream inputted from a digital broadcast signal receiving unit or a storage unit.
(2) Description of the Related Art
In recent years, it has become possible to enjoy, while watching TV, information such as news and weather on the Internet, pictures, and various objects such as subtitles and animations that are displayed in a video.
FIG. 19 is a diagram showing a conventional image synthesizing device (game system) 91.
The image synthesizing device 91 compares luminance differences between respective display target areas (911 and so on) defined on an image and a subtitle to be displayed with each other so that a graphics object is effectively displayed on the image, and determines a display area for the subtitle (see the first page, FIG. 1, and so on of Patent Reference 1 (Japanese Unexamined Patent Application Publication No. 2008-258929), for example).
The following describes the image synthesizing device 91.
In FIG. 19, the image synthesizing device 91 includes: a storage unit 920 that is a storage device such as a hard disk for storing, for instance, a program and data and a semiconductor memory element; a control unit 930 which includes, for example, a CPU (Central Processing Unit) and centrally controls a system; and an operation unit 940 which includes, for instance, an operation button to receive an input from a user. Moreover, the storage unit 920 includes: a game program storage unit 921 which holds a game program; a video information storage unit 922 which holds an image to be displayed on a monitor 950; a subtitle information storage unit 923 which holds subtitle information; and a subtitle display position storage unit 924 which stores a subtitle display area determined by the image synthesizing device 91. Furthermore, the control unit 930 includes: a game progress control unit 931 which properly reads out and executes the game program held in the game program storage unit 921; and a subtitle display control unit 932 which reads out the subtitle information held in the subtitle information storage unit 923, determines a display position, and displays a subtitle in the read subtitle information at the determined display position on the monitor 950
The following describes operations of the image synthesizing device 91 thus configured. The subtitle display control unit 932 reads out the subtitle information held in the subtitle information storage unit 923, and obtains a luminance value of the subtitle in the read subtitle information. The subtitle display control unit 932 obtains, for each image to be displayed, a luminance value of each of subtitle display areas 911 to 914 that are predetermined in the system, and evaluates luminance differences between the subtitle and the respective subtitle display areas 911 to 914. As a result, when the luminance difference between the subtitle and the subtitle display area becomes equal to or greater than a threshold, a subtitle display area having the luminance difference equal to or greater than the threshold is determined as a subtitle display area in which the subtitle is to be displayed.